How can we explain the development – or equally the non-development – of professional ethics norms in a particular case? And how can we enhance compliance with existing professional ethical norms? In this chapter, I develop a supply/demand theory of professional ethics. That is, I consider the demand-forces and pull-factors that call for the construction, reform or continuance of a professional ethos. These demands may come from various stakeholders, including individual service-providers, the professional community, actual and prospective clients and the general public collectively as interested third parties. The supply-side, on the other hand, constitutes the ethical materiel out of which norms emerge: these are the felt-motivations of individual professionals at the coalface of action that drive them to recognize, acknowledge and act upon a professional norm. This material includes traditions and stories, the conscious application of common-sense ethics, explicit endorsement of public moral codes, internal excellences within the activity, a discrete community capable of cultivating attractive role-identities and so on. As well as considering such ethical-materiel, I canvas the institutional and cultural supports that facilitate the production of these motives.